> CVE-2021-22390: Huawei NPU Kernel Driver Use-After-Free

Summary Due to a bug in the way mappings are closed it is possible to free a kmallocated memory chunk arbitrary times. This vulnerability can be used to craft a use after free scenario against any kernel structure that is allocated from the kmalloc-64 cache. There is rich public literature on how such use after free vulnerabilities can be utilized to compromise the kernel, achieve code execution in kernel context, and elevate privileges of user space processes. Even when modern mitigation is deployed. The mmap handler is exposed through the /dev/davinci0 character device. Due to the applied selinux policy, access to this device is restricted to the hiaiserver system process.